Waterproof Solar Battery Case

A number of people have asked about the best ways to keep their gear charging in wet situations like canoeing, rafting, and kayaking. It’s a tricky question because while our panels are waterproof–and will last outside for decades–batteries, and other portable electronics generally aren’t so lucky. Whether you’re kayaking across Glacier Bay, Alaska or winter camping in Mt. Rainier, Washington, your sensitive electronics and batteries should be housed in some kind of moisture proof case.

Then the question becomes: how do we get power from our outside panel to our battery and electronics inside of the case yet still maintain a waterproof seal?

Here’s a little tutorial we put together on one approach to solving the problem.

What we started with:

1 x Pelican Case — we used model 1050, but nearly any waterproof case should work.

1. Remove the rubber liner from the Pelican case and mark the spot to drill. This spot varies depending on application so it’s best to lay your products out before drilling or cutting to get an idea of how the wire will be routed inside the case. Try to lay it out so there are minimal bends in the extension wire.

2. DRILL! DRILL! DRILL! Actually, only drill once.

3. Slowly thread the cable gland into to the hole. Remember to try to keep it as square as possible so it’s not threaded in at an angle. If you’re really fancy you can tap threads into the hole, but it’s not necessary.

4. Tighten the cable gland into the case so that the rubber o-ring is slightly compressed, this should leave you with a small but workable amount of threads on the interior of the case.

5. Back the gland out of the hole and carefully trim down the excess plastic lip with a razor blade, retighten the gland and crew the M60 nut onto the back of the gland. Be careful not to over tighten the nut, it will only be gripping a couple threads.

6. Cut a hole in the rubber lining where the cable gland and nut are, and then refit it back into the case.

7. You’ll have to cut and resolder the extension cable because the ends won’t fit intact through the gland. It’s important you do a mock up so you’ll know how the parts will fit, prior to cutting the wire. Once you’ve mocked up the layout, cut the extension cable and strip with ends of the wires.

10. Loosen the exterior part of the cable gland and thread the longer end of the extension wire into the case.

11. To make sure this lasts, we soldered the ends, used electrical tape to insulate each connection, and then used heat shrink tubing. Don’t forget to put the tubing on before soldering the ends together… like I did the first time. Whoops.

12. Plug the female end of the extension cable into your panel, and the male end into your battery, then your battery into other devices like GoPro cameras, smart phones, or an Arduino (if you’re running a sensor project on your kayak).

!IMPORTANT!

Don’t forget to tighten the outer part of the gland to form the pressure seal on the extension wire… and don’t forget to close the case lid.

We tested this under running water for five minutes and there was no leaking. However we didn’t test it submerged because we don’t have a bath tub at Voltaic HQ (and the toilet was too small). But, we are taking it out this weekend on an actual kayak trip so we’ll report back if we have to make any modifications in the design.

2 Responses

We made a similar rig to power our video cameras and computer on a 30 canoe trip. The only difference was that our charger, panel and case were bigger units and we velcro’ed the panel to the case lid (trade off).

If I did it again, I would avoid keeping the wire on the side of the box, because it’s exposed to the world, can catch on tree branches, rip, whatever. That wire was a single point of failure for our film project and I carried it through a lot of forests and was paranoid the whole time.

If I had to do it again, I would cut the wire hole in the top of the peli case lid, fix the panel right on there and run it straight into the box with no exposed wires. I also would have cemented it onto the lid, but I understand why other people wouldn’t want to do this. You can see pictures here: